Question about metering with Canon 20D

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kotsana - 16 Mar 2006 23:05 GMT

When I use the evaluative metering, if I press and keep pressing the shutter
button halfway, the metering value is locked. So I can recompose the picture
as I want and take the picture with this metering value.
In partial metering or in centerweighted average metering, it's not possible
to do this. I notice that the metering value will change if I recompose the
picture.
Anybody knows why it's not possible to lock the metering value while using
this two modes ?

Thanks

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C J Southern - 16 Mar 2006 23:22 GMT

> When I use the evaluative metering, if I press and keep pressing the shutter
> button halfway, the metering value is locked. So I can recompose the picture
[quoted text clipped - 4 lines]
> Anybody knows why it's not possible to lock the metering value while using
> this two modes ?

I can't say why Canon have chosen this behaviour, but you should still be
able to achieve what you're after simply by using the AE Lock button.

It too works differently depending on which metering mode - In evaluative
mode it is applied to the AF point that achieved focus - on all other modes
it's applied to the centre AF point.

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Skip M - 16 Mar 2006 23:43 GMT

>> When I use the evaluative metering, if I press and keep pressing the
> shutter
[quoted text clipped - 17 lines]
> modes
> it's applied to the centre AF point.

Yeah, confused the devil out of me when I tried to lock exposure on my 5D on
spot. I mostly used eval. on my 20D, only occasionally using center
weighted, and I never used partial, so I never really noticed this behavior.
Weird choice, in my opinion.
And you're right, the exposure lock button does the trick. But I didn't
know that about the focus point, does that apply when using a manually
selected focus point? Geez, still learning, I didn't see any of this in the
manual...

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Skip Middleton
http://www.shadowcatcherimagery.com

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C J Southern - 17 Mar 2006 01:23 GMT

> And you're right, the exposure lock button does the trick. But I didn't
> know that about the focus point, does that apply when using a manually
> selected focus point?

I would have thought so, but I haven't tested it.

Geez, still learning, I didn't see any of this in the

> manual...

Page 149 of the 20D manual :)

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Skip M - 17 Mar 2006 06:12 GMT

>> And you're right, the exposure lock button does the trick. But I didn't
>> know that about the focus point, does that apply when using a manually
[quoted text clipped - 6 lines]
>
> Page 149 of the 20D manual :)

Wow, missed that one, and a couple of others. That's part of the problem
with learning on the fly, if you miss something, sometimes there's not time
to go back and re-read or re-learn it...

Signature

Skip Middleton
http://www.shadowcatcherimagery.com

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ian lincoln - 18 Mar 2006 22:43 GMT

>>> When I use the evaluative metering, if I press and keep pressing the
>> shutter
[quoted text clipped - 26 lines]
> selected focus point? Geez, still learning, I didn't see any of this in
> the manual...

I used the partial alot with the 20D. Lot better than holding and
recomposing.

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Skip M - 19 Mar 2006 04:20 GMT

>>> It too works differently depending on which metering mode - In
>>> evaluative
[quoted text clipped - 13 lines]
> I used the partial alot with the 20D. Lot better than holding and
> recomposing.

It covered too large an area for my comfort, I figured center weighted or
eval would work as well or better. But I was used to the 2% or 3% on my A2
and 1n and 1% on my handheld meter, so 9% seemed like a lot of acreage...

Signature

Skip Middleton
http://www.shadowcatcherimagery.com

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AaronW - 10 Apr 2006 06:38 GMT

> >>> When I use the evaluative metering, if I press and keep pressing the
> >> shutter
> >>> button halfway, the metering value is locked. So I can recompose the
> >> picture
> >>> as I want and take the picture with this metering value.

This also has disadvantage. After recomposing, the final scene is
different from the metered scene. So I disabled AE locking, i.e., AE is
not locked by half pressing the shutter button, but done at shutter
release time.

> >>> In partial metering or in centerweighted average metering, it's not
> >> possible
[quoted text clipped - 12 lines]
> >> modes
> >> it's applied to the centre AF point.

Maybe they don't want to confuse people, whether "center" metering
means center of the frame, or centered on the AF point. Besides, when
several AF points are locked, which one should be the "center" for
metering?

> > Yeah, confused the devil out of me when I tried to lock exposure on my 5D
> > on spot. I mostly used eval. on my 20D, only occasionally using center
[quoted text clipped - 7 lines]
> I used the partial alot with the 20D. Lot better than holding and
> recomposing.

What do you mean? To use partial metering, don't you have to hold AE
Lock to spot meter and then recompose?

http://digitcamera.tripod.com/#slr

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ian lincoln - 10 Apr 2006 07:18 GMT

"AaronW" <bj286@scn.org> wrote in message >> I used the partial alot with
the 20D. Lot better than holding and

>> recomposing.
>
> What do you mean? To use partial metering, don't you have to hold AE
> Lock to spot meter and then recompose?

permanently select partial. Then use the focusing points to select the
area.

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kotsana - 17 Mar 2006 08:26 GMT

> > When I use the evaluative metering, if I press and keep pressing the
> shutter
[quoted text clipped - 15 lines]
> mode it is applied to the AF point that achieved focus - on all other modes
> it's applied to the centre AF point.

Yes, I can use the AE Lock button but it's easier to use to use a single
button like in eval ...
Thanks.

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